Heart period variability in trauma patients may predict mortality and allow remote triage

The high frequency to low frequency ratio (HF/LF) derived from analysis of heart period variability is elevated and associated with mortality in severely injured patients monitored in a hospital. The purpose of this study was to test the utility of heart period variability measurements as indicators of injury severity in patients prior to definitive medical intervention. We tested the hypothesis that survival is associated with low relative HF/LF, and death is associated with high relative HF/LF.

We performed retrospective analyses of 84 pre-hospital trauma patient records (n=42 non-survivors; n=42 survivors) collected during helicopter transport to a Level 1 urban trauma center. R-waves from 2-min segments of ECG waveforms were converted to the frequency domain with a Fourier transform. Spectral power was separated into low (LF; 0.04-0.15 Hz) and high (HF; 0.15-0.4 Hz) frequency bands for analysis and derivation of frequency ratios.

Absolute HF, LF, and HF/LF were not distinguishable statistically between groups (p > or = 0.26), but HF/LF was higher (p = 0.04) for non-survivors (140 +/- 26) than survivors (74 +/- 19). After normalization to account for large intersubject variability, HFnu (43 +/- 3 vs. 28 +/- 2) and HF/LFnu (248 +/- 50 vs. 73 +/- 19) were higher (both p < 0.001), and LFnu (42 +/- 4 vs. 64 +/- 3) was lower (p = 0.0001) for non-survivors [19 h (median) before death] compared with survivors.

Our results show that heart period variability analyses separate patients who die from patients who survive traumatic injury. We propose that such analyses could be employed for remote triage of injured patients in austere environments.